package com.icss.trans.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.apache.log4j.Logger;

/**
 * <p>
 * Title:
 * </p>
 * <p>
 * Description:
 * </p>
 * <p>
 * Copyright: Copyright (c) 2011
 * </p>
 * 
 * @author <a href="mailTo:zhangjie@chinasofti.com">zhangjie</a>
 * @version 1.0
 * @history: Created by zhangjie 2011-8-23
 */

public class MD5Util {

    private static final Logger log = Logger.getLogger(MD5Util.class);

    /**
     * 默认的密码字符串组合，apache校验下载的文件的正确性用的就是默认的这个组合
     */
    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e',
            'f' };

    protected static MessageDigest messagedigest = null;
    static {
        try {
            messagedigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            log.error("init failed,MessageDigest does not support MD5Util.");
            log.error(e.getMessage());
        }
    }

    /**
     * @param file
     * @return md5 String
     * @throws IOException
     */
    public static synchronized String getFileMD5String(File file) throws IOException {
        FileInputStream in = new FileInputStream(file);
        try {
            byte buffer[] = new byte[(int) file.length()];
            in.read(buffer);
            messagedigest.update(buffer);
            // FileChannel ch = in.getChannel();
            // MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
            // messagedigest.update(byteBuffer);
            return bufferToHex(messagedigest.digest());
        } catch (IOException ex) {
            throw ex;
        } finally {
            if (in != null)
                in.close();
        }
    }

    /**
     * @param file
     * @return md5 String
     * @throws IOException
     */
    public static String getFileMD5String(File file, int i) throws IOException {
        FileInputStream in = new FileInputStream(file);
        try {
            byte buffer[] = new byte[i];
            in.read(buffer);
            messagedigest.update(buffer);
            // FileChannel ch = in.getChannel();
            // MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
            // messagedigest.update(byteBuffer);
            return bufferToHex(messagedigest.digest());
        } catch (IOException ex) {
            throw ex;
        } finally {
            if (in != null)
                in.close();
        }
    }

    /**
     * 适用于上G大的文件
     * <p>
     * Description:当文件变大时将数据全部读入内存计算MD5值，目前将数据读入到4k缓存中逐个更新加密串，该算法能保证同一个文件得出的加密串是相同的，单不能保证唯一性
     * <p>
     * 
     * @param file
     * @return
     * @throws IOException
     * @author zhangjie 2011-8-26
     */
    public static String getDeFileMD5String(File file) throws IOException {
        FileInputStream in = new FileInputStream(file);
        try {
            byte buffer[] = new byte[4096];
            while (in.read(buffer) != -1) {
                messagedigest.update(buffer);
            }
            return bufferToHex(messagedigest.digest());
        } catch (IOException ex) {
            throw ex;
        } finally {
            if (in != null)
                in.close();
        }
    }

    public static String getMD5String(String s) {
        return getMD5String(s.getBytes());
    }

    public static String getMD5String(byte[] bytes) {
        messagedigest.update(bytes);
        return bufferToHex(messagedigest.digest());
    }

    private static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];
        char c1 = hexDigits[bt & 0xf];
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

    public static boolean checkPassword(String password, String md5PwdStr) {
        String s = getMD5String(password);
        return s.equals(md5PwdStr);
    }

}
